package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;
import com.lagou.utils.TokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1.注册驱动，获取链接
        Connection connection = configuration.getDataSource().getConnection();

        //2.获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象 prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
        String paramType = mappedStatement.getParamType();//获取到了参数的全路径
        System.out.println("paramType------->"+paramType);
        Class<?> paramterTypeClass = getClassType(paramType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            System.out.println("content---->"+content);

            //反射 根据参数名称获取实体对象中的属性值
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);

        }
        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        Object o = resultTypeClass.newInstance();
        ArrayList<Object> objects = new ArrayList<>();

        //6.封装返回结果集
        while (resultSet.next()){
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount() ; i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object object = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,object);

            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    private Class<?> getClassType(String paramType) throws ClassNotFoundException {
        if(paramType != null) {
            Class<?> aClass = Class.forName(paramType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？代替，2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }
}
